1 Technical Field
This disclosure relates generally to a spark plug.
2 Background Art
Japanese Patent First Publication No. 2016-51635 discloses a spark plug which is equipped with a cylindrical center electrode and an annular ground electrode. The ground electrode is disposed to have an inner peripheral surface facing an outer peripheral surface of the center electrode. The ground electrode has a front end which is located farther away from a base end of the spark plug than a front end of the center electrode is. This facilitates concentration of electric field on the outer peripheral surface of the center electrode, thus resulting in a decrease in voltage required to create discharge in the spark plug.
The spark plug, as taught in the above publication, has the front end surface of the ground electrode which is located closer to the front side of the spark plug than the front end surface of the center electrode to concentrate the electric field on the front end of the outer peripheral surface of the center electrode. It is, however, required to further decrease the voltage required to create discharge in the spark plug. There is, thus, still room for improvement in the structure of the spark plug.